Flexible conductor



May 1941 E. E. scHuMAcHER ETAL y2,240,579

FLEXIBLE' CONDUCTOR Filed NOV. 5. 1938 COPPER HERYLL /UM ALLOY m ,y m E N N ME RM uw o wo m $5 Erm EA.

/N VEN TORS Patented May 6, 1941 'I'his invention relates to flexible conductors and more particularly to an improved tinsel thread for use in flexible conductorsV such as those employed in telephone cords.

In order to provide a satisfactory telephone cord it is not only essential that the individual conductors have the required flexibility and electrical conductivity but they must also be capable of retaining these characteristics even under severe service conditions for the entire period of their useful life. To replace a telephone cord a special trip to the subscribers station is necessary and, accordingly, the cost of replacement is often quite large in comparison to the cost of the cord per se. It is therefore desirable that a long life is assured.

It is therefore the principal object of this invention to produce a. flexible conductor having the desired electrical and physical characteristics and one in which these characteristics will remain constant for a greater period of time than has been possible heretofore.

In accordance with one or more features of the present invention this object is attained by the uselof a plurality of tinsel conductors twisted tallic ribbons helically wrappedabout a textile core. copper-beryllium alloy containing from .5 to 2.5 per cent of beryllium and so treated as to have not only the desired physical and electrical characteristicsbut also to retain these characteristics over a long period of life when subjected tothe repeated bending and twisting action that such conductors receive under certain service conditions.'

In the single ilgure of the drawing there is dis closed one embodiment of the invention in which a plurality of tinsel threads are twisted together about a textile core to provide an electrical conductor in accordance with the invention.

Referring to this drawing, six conducting elements or tinsel threads 5-5 are stranded about a textile core member i to form a complete conductor. An inner cotton braid 1 is woven about this conductor and over this is woven an outer braid 8 which carries colored tracer threads I which are used to identify the various conductors y oi' a complete corti.` Each of the individual tinsel threads is shown as composed of two metallic ribbons Ill-i0 served in an open helix about the textile core Il. proximately .017 inch wide and .0008 inch thick, are rolled down from No. 37 AWG wire or drawn the construction of the conductors be such that' 'I'hese metallic ribbons are composed of a These ribbons, which are ap' together and each composed of one or more meductors.

UNITED STATES PATENT OFFICE FLEXIBLE CONDUCTOR Earle E. Schumacher, Maplewood, and Alexander G. Sonden, Jersey City, N. J., assignors to Bell Telephone Laboratories, Incorporated,l New York, N. Y., a corporation of New York Application November 5, 1938, Serial No. 238,978

3 Claims. 174-131) to these dimensions from larger size wire and are composed of a copper-beryllium alloy, the beryllium content of which is preferably about 1% per cent although conductors having improved characteristics are obtained when the beryllium content of' the ribbon is not less than .5 per cent and not more than 21/2 per cent.

It has been found that to obtain the maximum improvements in the characteristics of the con--I ducting ribbons they should be subjected to both dispersion hardening and cold working. The preferred method of treating these alloys is as follows:

The alloy in the form of M4 inch rods is ilrst subjected to a softening treatment by'maintaining it at a temperature of approximately 800 C. for a period of two hours, followed by quenching. The material then is cold drawn down to No. 33 AWG wire and during this reduction it is preferably softened after each reduction of four AWG numbers. When the wire has been drawn down to No. 33 gauge it is given a dispersion hardening treatment at approximately 375 C. for four hours in a purified hydrogen atmosphere and then water quenched. It is then cold drawn down to No. 37 gauge wire, after'which it is cold rolled to ribbons approximately ..0009 inch thick and .017 inch wide. Satisfactory results have been obtained using a softening temperature of from 800 C. to 1000 C., depending upon the particular alloy, and a dispersion'hardening temperature of 250 C. to 500 C.

In the following table are given the results of tests on various copper-beryllium alloys in the form of No. 37 AWG wire treated as disclosed above and compared with similar samples of a copper-tin alloy in common use vfor tinsel con- This table also gives the results of tests showing the bending fatigue resistance of ribbons of these materials of the size specied when bent about a steel arbor having a radius of .02 inch.

tullio ribbon helicelly wound thereupon und composed oi' an nlloy containing approximately 11% per cent beryllium and the belence copper. such |.lloy'lmviuz` the physical characteristics produced by bein: dispersion hardened followed by cold working.

2. A time! thread for electrical conductors 4consieizingofetextilecore:member-havingemeribbon tellic hellcelly wound thereupon composed oi' o copper-beryllium alloy consisting of from 1% to 1% per cent beryllium and the belonce copper and having e conductivity not less than m'per cent that o! pure copper.

.3. A tinsel thread for electrica. cfm-z w comprising l. textile core member and a ribbon approximately .0009 inch thick :n J inch wide, said ribbon being composed of e msofper centberyiliumendthebelsncecopper.

and having o conductivity not lees than 30 per cent that o! pure copper.

BARI: E. ALEXANDER G. BOUDDI. 

